Dual drill stem method and apparatus



Jan. 10, 19 7 s. H. CREWS 3,297,100

DUAL DRILL STEM METHOD AND APPARATUS Filed April 15, 1964 4 Sheets-Sheetl INVENTOR. SIM H. CREWS A T TOQA/EYS Jan. 10, 1967 S. H. CREWS DUALDRILL STEM METHOD AND APPARATUS 4 Sheets-Sheet 2 Filed April 13, 1964Jan. 10, 1967 s. H. cREws 3,297,100

DUAL DRILL STEM METHOD AND APPARATUS Filed April 13, 1964 4 Sheets-5heet15 M H CREWS S. H. CREWS DUAL DRILL STEM METHOD AND APPARATUS Jan. 10,1967 4 Sheets-Sheet 4.

Filed April 13, 1964 WW VM 7 INVENTOR. $1M H CREW S United States Patent3,297,100 DUAL DRILL STEM METHOD AND, APPARATU Sim H. Crews, Mercury,Nev., assignor to Large Mine Shaft Drillers, incorporated, Amarillo,Tern, a corporation of Texas Filed Apr. 13, 1964, Ser. No. 359,214 2Claims. Cl. 175-195) This invention relates to improved methods andapparatus for drilling holes downwardly into the earth, and especiallyto the rotary drilling of relatively large diameter mine shafts and thelike.

It is a well developed practice in forming both small and large diameterwells to drill into the earth with a rotating bit secured at the lowerend of a string of rods or drill pipe while earth cuttings produced bythe bit are flushed to the surface and removed from the well bore byliquids, gases or combinations thereof under controlled pressures. Inthe past several years, however, additional development work has led toimproved drilling rates and lower costs for drilling relatively smalldiameter wells such as those used in the production of water, gas andoil. This development work has centered upon increasing the weight orpressure applied to cutting bits and utilizing increased pneumatic orhydraulic flow rates and volumes in the well bore for keeping the holeface clean and lifting larger bit cuttings to the surface.

The application of such increased bit pressure in relatively largediameter shaft boring has been accomplished reasonably well, However,the application of sufficient hydraulic and/or pneumatic flow rates andvolumes in large diameter bores for continually cleaning the hole faceand carrying bit cuttings to the surface has heretofore not beenaccomplished. This has been somewhat due to the prohibitively high fluidvolumes involved, but in greater measure to the excessively high powerrequirements and quantity of pumping equipment necessary to produce highenough return flow velocities in the drill stem-well bore annulus tolift reasonably large bit cuttings while providing high pressure bottomjets to clean the hole face.

The principal objects of the present invention are: to provide a methodand apparatus for drilling larger diameter holes which utilizes a dualdrill stem forming two conduits in addition to the drill stem-well boreannulus; to provide such a method and apparatus wherein one of theconduits may be used to conduct a fluid to the bit with sufiicientpressure to cleanse the hole face with high pressure bottom jets and thesecond conduit may be used to conduct a high volume-relatively lowpressure fluid into the drilling area to improve the drill stemwell boreannulus fluid return velocities; to provide such a method and apparatuswherein the second conduit may alternatively be used to conduct thefluid back to the earth surface with the required velocity for liftingrelatively large bit cuttings; to provide such a method and apparatuswhich permits the application of greater weight for producing a higherpenetration rate with a consequent reduction in drilling costs; toprovide such a method and apparatus which permits the rapid andconvenient application and removal of a dual fluid passage bit, a dualfluid passage drill collar string, a dual fluid passage drill pipestring, and a dual fluid passage kelly for producing relatively largediameter earth holes such as mine shafts; to provide in the practice ofrotary drilling dual drill string apparatus so constructed thatconcentric inner 3,297,160 Patented Jan. 10, 1967 and outer pipes may berespectively easily joined and removed for insertion into and removalfrom the well bore; to provide such a dual drill string apparatuswherein joints of inner pipes project above respective lower joiningcollars of the respective outer pipe open joint so that the inner pipesmay be held securely while being joined or uncoupled from succeedinginner pipes; to provide such apparatus wherein the respective dualstring inner pipes are of approximately the same length as the outerpipes and are concentrically spaced therewithin by means of wings orspacers extending into the passageway between the outer and inner pipes;to provide such apparatus wherein the inner pipes are free to movelongitudinally within the outer pipes so as to permit easy exposure ofthe inner pipe joints as Well as complete removal of the inner pipesfrom the outer pipes when desired; to provide unique accessory tools tofacilitate the handling and joining of the relatively movable inner andouter pipes of a dual drill string section; and to provide such a methodand apparatus which is relatively simple in construction, versatile inoperation and yet highly effective in use.

Other objects and advantages of this invention will become apparent fromthe following description taken in connection with the accompanyingdrawings wherein are set forth by way of illustration and examplecertain embodiments of this invention.

FIG. 1 is a partially schematic sectional view in side elevation showingwell drilling apparatus incorporating a preferred embodiment of thisinvention.

FIG. 2 is a vertical cross-sectional view on a larger scale showing adual pipe string section engaged with a male pipe thread protector atthe lower end thereof.

FIG. 3 is a vertical cross-sectional view on a scale similar to FIG. 2showing a dual pipe string section engaged with an inner tube suspendingplug at the upper end thereof.

FIG. 4 is a cross-sectional view through a dual pipe section taken onthe line 4-4, FIG. 2, showing particularly wings or spacers forcentering the inner pipe,

FIG. 5 is a fragmentary vertical cross-sectional view through a dualpipe section joint on a scale similar to FIG. 2 illustrating an outerpipe joint as uncoupled and exposing the adjacent inner pipe joint.

FIG. 6 is a vertical cross-sectional fragmentary view on a scale similarto FIG. 2 particularly illustrating a drill bit adapted for use inaccordance with this invention. I FIG. 7 is a fragmentary verticalcross-sectional view on a scale larger than that of FIG. 2 illustratinga telescoping inner tube joint contained within the drill string drivestem or kelly.

FIG. 8 is a vertical fragmentary view showing a modified form of swivelhead assembly in the drilling position.

FIG. 9 is a vertical fragmentary view showing the modified swivel headof FIG. 8 in connecting or inner pipe joint exposed position.

FIG. 10 is a vertical cross-sectional partially schematic viewillustrating another form of drill bit adopted for use in accordancewith this invention.

Referring to the drawings in more detail:

The reference numeral 1, in FIG. 1, generally indicates a drillingapparatus particularly adapted for boring relatively large holes orshafts, for example in the order of lO-feet in diameter. The drillingapparatus 1 is illustrated in conjunction with a shaft or bore 2, aportion of which is protected by a well casing 3 having a well head 4thereon. The drilling apparatus 1 includes a vertical elongated dualdrive stem or kelly 5 which extends downwardly through the well head 4and makes a vertically sliding seal therewith in a well known manner. Arotary drive table 6 is located above the well head 4 and the kelly 5extends therethrough. The kelly 5 terminates at the upper end 7 thereofin a swivel head 8 having a bail 9 by which the kelly is verticallysupported.

The kelly 5 comprises an outer generally square pipe 10 which engageswith the rotary drive table 6 and well head 4 and an inner circular pipe11 of smaller diameter than the inside dimensions of the kelly outerpipe 10 and extending longitudinally within the outer pipe 10. The pipes10 and 11 form inner and outer concentric flow passageways 12 and 13respectively within the kelly 5. The swivel head 8 includes an innergooseneck 14 communicating with the kelly inner passageway 12 and anouter gooseneck 15 surrounding a portion of the inner gooseneck 14 andcommunicating with the kelly outer passageway 13 in a known manner, theswivel head remaining rotationally stationary when the kelly is rotatedby the drive table 6.

The kelly outer pipe 10, in the illustrated example, terminates at thelower end 16 thereof in a threaded drill pipe string pin collar 17having tapered screw threads 18 of the rapid pitch type. The kelly innerpipe 11 terminates at the lower end 19 thereof in a threaded conduitpipe string pin collar 20 having tapered screw threads 21 of the rapidpitch type. The kelly inner pipe 11 includes a telescoping sealed joint22 spaced between the swivel head 8 and the pin collar 20, FIG. 7. Thejoint 22 is comprised of an intermediate coupling portion 23 threadedlyengaged at the lower end thereof in a packing collar 24 containingsuitable chevron packing 25 and at the upper end thereof in a connectorsection 26. The coupling portion 23 slightly reduces in diameterintermediate the ends thereof forming an interior upwardly facingshoulder 27 adapted to engage an arresting flange 28 on an innertelescoping tube 29 slightly engaging the packing 25 and which supportsthe pin collar 20. Thus, the pin collar 20 is permitted to be axiallypositioned between a first or exposed position illustrated by the brokenlines at 30 spaced below the kelly outer pipe pin collar 17 and a secondor withdrawn position as illustrated in solid lines at 31 spaced abovethe kelly outer pipe pin collar 17.

The drilling apparatus 1 includes a vertically extending dual pipestring 32 comprising a plurality of connected outer or drill stringpipes 33 and a plurality of connected inner or conduit string pipes 34of smaller outside diameter than the inside diameter of the drill stringpipes 33 and contained therewithin. The drill string pipes 33 eachterminate at the upper end 35 thereof in a threaded drill string boxcollar 36 having tapered rapid pitch threads 37 thereon and at the lowerend '39 thereof in a threaded drill string pin collar 40 having taperedrapid pitch threads 41 thereon adapted to threadedly engage with the boxcollar 36 of an adjacent drill string pipe 33. The drill string pipes 33are joined in a string 42 by mating succeeding drill string box and pincollars. The uppermost drill string box collar is joined to the kellydrill string pin collar 16 for suspending the drill pipe string 42 fromthe swivel head 8.

The conduit string pipes 34 each terminate at the upper end 43 thereofin a conduit string box collar 44 having tapered rapid pitch threads 45therein and at the lower end 46 thereof in a conduit string pin collar47 having external tapered rapid pitch threads 48 thereon. The conduitstring pipes 34 are respectively joined in a string 49 within the drillpipe string 42 by mating succeeding conduit pipe box and pin collars.The uppermost conduit pipe box collar is mated to the pin collar 20 ofthe kelly 5 and, as noted further hereinafter, causes the kelly innerpipe joint 22 to telescope upon the breaking or mating of the joint 50formed at the kelly outer pipe lower end 16. The drill pipe string 42and concentric conduit pipe string 49 form inner and outer concentricflow passageways 51 and 52 respectively communicating with the kellyflow passageways 12 and 13.

The conduit string pipes 34 each have, in the illustrated example, threeradially outwardly extending guides or wings 53 fixed thereto adjacentthe box collars 44 thereof and extending into the outer flow passageway52. The guides or wings 53, however, present a relatively thin profilein cross-section and, therefore, do not significantly block flow throughsaid passageway. The guides or wings 53 terminate at outer ends 54 atrespective outer radial dimensions or positions which produce thecentering of the respective conduit pipe 34 within the respective drillstring pipe 33 but permit a relative longitudinal sliding movementtherebetwcen.

A dual fluid passage drill bit 55 is located at the bottom of or axiallybeneath the dual pipe string 32. The bit 55 comprises a housing 56having a frusto-conical side wall 57 of greater diameter at the bottom58 thereof than at the top 59. The housing 56 includes spaced-apartupper and lower walls 61} and 61 secured thereto adjacent the respectivetop 59 and bottom 58 and forming with the side wall 57 an enclosedfrusto-conical chamber 62. The housing upper wall 60 extends radiallyhorizontally outwardly from the top of the housing forming a couplingflange 63 for a purpose noted hereinafter. The housing lower wall '61has a plurality of downwardly extending legs 64 secured thereto andrespectively rotatably supporting at the lower ends thereoffrusto-conical rotatable cutters 65 of known design. A plurality oftubes 66 are mounted in and extend through the housing lower wall 61 andform passageways 67 communicating between the chamber '62 and theexterior of the housing 56. The tubes 66 are respectively positioned fordirecting fluid flow in jets from the chamber 62 downwardly adjacent therespective cutters 6-5 for maintaining the cutting field clear ofcuttings or debris, as discussed more fully hereinafter.

An outer vertically extending length of pipe 68 is secured at the lowerend 69 thereof in dawnwardly abutting relation to the housing lower wall61 and extends coaxially upwardly within the chamber 62. The length ofpipe 68 extends into the housing upper wall 60 and terminates at theupper end 70 thereof at the elevation of the upper surface 71 of thecoupling flange 63. A plurality of radially outwardly and downwardlyextending bores 72 extend through the length of pipe 68 intermediate theends thereof providing flow passageways communicating between thechamber 62 and the interior 73 of the length of pipe 68. An inner lengthof pipe 74 of smaller outside diameter than the inside diameter of thelength of pipe 68 extends coaxially therewithin and also extendsdownwardly through and is fixed to the housing lower wall 61 forming anopen mouth 75 at the lower surface 76 of the housing lower wall 61. Theinner length of pipe 74 terminates at the upper end 77 thereof in aconduit string box collar 78 spaced above the coupling flange uppersurface 71 and threadedly receiving the lowermost condit string pincollar 79 on the conduit string 49, thus providing communication betweenthe mouth 75 and the inner concentric flow passageway 51.

A safety joint 80 is located between the ends of the inner length ofpipe '74 to produce a separation of the conduit pipe string 49 adjacentthe lowest part thereof, that is, within the drill bit 55 in case anexcessive torque is applied on the conduit pipe string 49.

A drill collar 81 comprises a tube 82 of similar diametrical dimensionsas the body of the drill string pipes 33 and has a radial couplingflange 83 fixed to the lower end thereof which matches and is bolted tothe bit coupling flange 63. A suitable ring seal 84 is located betweenthe respective flanges 83 and 63 in high pressure contact caused by thebolts 85 urging the respective coupling flanges toward each other. Thering seal 84 prevents the escape of fluid from between said latterflanges.

The drill collar tube 82 terminates at the upper end 86 thereof in adrill string pipe box collar 87 which is spaced below the box collar 88on the lowermost conduit string pipe 89, that is, the inner pipe coupledto the drill bit inner length of pipe 74. The box collar 87 threadedlyreceives the lowermost drill string pipe pin collar 90 for supportingand driving the drill bit 55 and producing communications between theouter flow passageway 52 and the chamber 62.

Tubular or ring-shaped weights 91 have an inside diameter slightlygreater than the outside diameter of the drill collar tube 82 and aretelescoped over said latter tube and rest on the drill collar flange 83for transmitting the weight thereof to the drill bit 55. The weights 91may be suitably coupled together by bolts such as at 92 and theuppermost weight 91, in the illustrated example, has a conical-shapedupper surface 93 to aid in withdrawing the drill bit from the shaft orbore 2 with a minimum of interference.

The threads joining the respective outer or drill string pipes 33 are ofopposite hand from the threads joining the inner or conduit string pipes34 whereupon the conduit string may be rotated by the drill stringthrough the bit rather than directly from the kelly outer pipe 10. Therespective conduit string pipes 34 and drill string pipes 33 are ofsubstantially equal length whereby each conduit string pipe box collar44, that is the upper end of each conduit string pipe 34, extends abovethe corresponding drill string pipe box collar 36. This is due to therelative positions of the respective conduit and drill string boxcollars 78 and 87 associated with the bit inner length of pipe 74 andthe drill collar 81. Thus, as described more fully below, as the dualpipe string is assembled and disassembled, the respective conduit stringpipe joint is exposed for grasping and manipulation as best illustratedin FIG. 5.

Referring to FIGS. 2 and 3, two accessory tools are depicted which areuseful in the practice of this invention. They are respectively a malepipe thread protector 94 and an inner tube suspending plug 95. Theprotector 94 is in the shape of an inverted cap having an internalthread 96 adapted to threadedly engage the respective drill string pincollar 44]. The protector 94 includes an upwardly projecting inner cone97 terminating in a shoulder 98 and pin 99 for receiving the respectiveconduit string pin collar 4-7 and positioning same so that the conduitstring pipe 34 is, with the aid of the wings 53, centered within thedrill string pipe 33 and the conduit string box collar 44 is spacedabove the drill string pipe box collar 36. The protector 9 preferablyincludes a central bore or passageway 100 through which a cable or othersuspending member (not shown) may be inserted for handling the dual pipesection.

The suspending plug 95 comprises a cap member having a tapered andradially extending flange portion 101 adapted to be axially received ina drill string box collar 36 but not pass therethrough. The suspendingplug 95 includes an inner depending pin 192 having tapered threads 153at the lower end thereof for threadedly receiving a conduit string boxcollar 44 for suspending a conduit stringpipe 34 Within a drill stringpipe 33 in a position whereby the conduit string pin collar 47 projectsbelow the respective drill string pin collar 40. The suspending plug 95includes a suitable bore or passageway 104 through which a cable orother suspending member (not shown) may pass for convenience inhandling. The utility of the thread protector 94 and suspending plug 95is noted below.

In conducting a drilling operation, the drill bit 55 is placed on ahorizontal surface with the cutters 65 extending downwardly. In thisposition, the inner length of pipe 74 extends above the coupling flange63. The drill collar 81 is picked up. When picked up, the drill collar81 contains therewithin a conduit string pipe 34 suspended by asuspending plug 95 which causes the respective conduit pipe pin collar47 to project below the drill collar coupling flange 83. With the boxcollar 78 on the bit pipe '74 projecting freely upwardly and the conduitstring pipe pin collar 47 projecting freely downwardly from the couplingflange 83, the respective box and pin collars are easily grasped byknown tools to form a joint therebetween. The drill collar is thenlowered and the coupling flange 83 bolted to the coupling flange 65 ofthe bit 55. The lowering of the drill collar 81 causes the upper end orbox collar 88 of the first conduit string pipe 34 to project above thebox collar 87 of the drill collar 81. The weights 91 may be telescopedover the drill collar 81 at this time or prior to lifting the drillcollar as desired. The bit and drill collar assembly is then loweredinto the shaft or bore 2 until the upper end of the drill collar ispositioned at the upper surface of the rotary drive table 6, suitableconventional slips (not shown) being used to suspend same therefrom.

The inner tube suspending plug 95 is then removed from the first conduitstring pipe and placed in the next dual string section to be installed.The male pipe thread protector 94, which is used in storing the loosedual string sections, is removed, thus permitting the conduit pipe 34 toextend below the lower end of the respective drill pipe 33 as the innertube suspending plug 95 engages the drill string pipe box collar 36. Thedual pipe section is then suspended over the center of the drive table 6and because the upper and lower portions of the inner coupling areexposed as in FIG. 5, they are easily grasped for joining. The suspendeddrill string pipe 33 is then lowered to the position illustrated by thebroken lines 155 (FIG. 5) and joined to the adjacent drill pipe boxcollar (either on the drill collar 31 or preceding drill pipe 33). It isapparent that as each dual pipe section is added, the upper end or boxcollar of the conduit pipe will be exposed for joining to a subsequentexposed lower end or pin collar of a conduit pipe 34 suspended fromWithin a drill pipe 33.

' The joining operation continues until the bit reaches the bottom orface 106 of the shaft or bore 2 and then the dual drive stem or kelly 5is connected to the uppermost conduit pipe 34 and drill pipe 33 in thesame manner. When the kelly outer pipe 10 is lowered to threadedlyengage the uppermost drill pipe box collar as, the telescoping sealedjoint 22 takes up the necessary longitudinal displacement of the kellyinner pipes 11. The slips (not shown) are removed in the normal mannerfrom the drive table 5 and a conventional drive bushing 1t inserted toproduce the driving engagement between the table 6 and the outer kellypipe 10.

During the drilling operation, liquids, gases and/or mixtures of thesefluids may be forced in various paths through the inner flow passageway51, outer flow passageway 52 and the bore-drill pipe annulus 108. As apreferred example, a suitable drilling liquid may be pumped through theouter gooseneck 15 downwardly through the outer flow passageway 52 inthe path illustrated by the arrows 1% at high pressure to produce veryhigh velocity but relatively low volume jets 110 issuing from the tubes56 which keeps the bottom or face 106 of the bore 2 washed free ofcuttings for maximum drilling speed. The relatively low volume issuingfrom the tubes 66 is, however, insuflicient to produce the necessaryvelocity in the bore-drill pipe annulus 108 to lift the relatively largecuttings to the surface which is necessary for efficient drilling. Inorder to sufficiently increase the liquid velocity in the annulus 108, alarge volume of drilling liquid is forced at relatively low pressuresthrough the inner gooseneck 14, down the inner flow passageway 51, andout the open mouth 75 at the bit, as illustrated by the arrows 111,which latter fluid when combined with the jetting fluid produces thedesired upward flow velocity in the annulus 108. The fluid in theannulus 108 subsequently issues from a pipe 112 communicating throughthe well head 4 at the surface. In one alternative flow pattern,,itmight be desirable to greatly reduce the total volume of drilling liquidused but maintain sufficient velocity for carrying relatively largecuttings to the surface. In the latter case, a relatively high butgenerally static gas or liquid pressure may be maintained through thepipe 112 in the annulus 108 and the cuttings forced upwardly through theopen mouth 75 and inner flow passageway 51 and out the inner gooseneck14, the drilling liquid being pumped at high pressure and relatively lowvolume downwardly through the outer flow passageway 52.

During the drilling operation, the bit driving torque is transmitted bythe rotary drive table 6 to the kelly outer pipe 10, drill pipe string42 and drill collar 81 to the bit 55 and the conduit pipe string 49rotates therewith passively through the connetcion with the bit innerpipe 74. The conduit pipe string 49 may rotate with respect to thestationary swivel head 8 either within the swivel head itself or withinthe telescoping joint 22 as desired. As noted above, the couplingthreads on the drill pipe string are of opposite hand from the conduitpipe string to permit the above driving configuration without unscrewingthe respective joints. It is to be understood, however, that othercoupling configurations with or without threaded connectors may be usedwithout departing from the scope of this invention. In making up orbreaking apart the dual drill string apparatus and during the drillingoperation, the guides or wings 53 maintain the inner conduit pipessubstantially concentrically positioned within the drill pipes but donot interfere with the longitudinal sliding therewithin for exposing theinner conduit pipe joints. It will be appreciated that upon the removaland breaking apart of the dual drill stem the outer or drill pipe jointis first unscrewed and separated which exposes the inner or conduit pipejoint for grasping in order to properly unscrew. Further, if it isdesired to remove the inner or conduit string from the drill pipestring, it is not necessary to break apart the respective joints of thedrill pipe string, but rather the conduit string may be independentlyrotated for breaking the safety joint 80 whereupon the inner or conduitstring may be lifted longitudinally without disturbing either the bit,drill collar or drill pipe string. Persons skilled in the drilling artwill appreciate that other materials rather than drilling fluids may bepumped through the passageways abovedescribed, for example, compositionsfor cementing or plugging a shaft.

A modified form of swivel head assembly or dual kelly structure isillustrated in FIGS. 8 and 9 and differs from the kelly structuredescribed above in the means for obtaining a variation in relative axialpositioning of the pin collar 113 on the kelly inner pipe 114 withrespect to the pin collar 115 of the kelly outer pipe 116. FIG. 8illustrates the kelly structure in drilling position with the kellyinner pipe pin collar 113 urged upwardly past the outer pipe pin collar115 by the inner pipe box collar 117 on the inner pipe string inresponse to engagement of the outer pipe box collar 118 with the outerkelly pipe pin collar 115. Instead of a telescoping joint 22 asdescribed above (FIG. 7) the upward displacement of the pin collar 113in the embodiment of FIGS. 8 and 9 is permitted by slidably displacingthe entire kelly inner pipe 114 upwardly through a suitable sealstructure 119 in the outer pipe gooseneck swivel assembly 120. The innerpipe gooseneck swivel assembly 121 is conventional except for freedom ofvertical displacement with respect to the swivel assembly 120, referringto FIG. 9 the modified kelly structure is shown with the inner pipecollars 113 and 117 exposed in which position the inner pipe gooseneckswivel assembly may rest upon the seal structure 113 to support thekelly inner pipe 114.

An additional dual passageway drill bit configuration is illustrated inFIG. and comprises a body or housing 122 rotatably supporting threetiers of bits or cutters 123, 124, and 125 on respectively greaterradii. An interior passageway 126 extends downwardly through the body orhousing 122 and enlarges at 127 and 127 forming chambers whichcommunicate respectively with discharge tubes 128 and 129. The tubes 128and 129 open at the contact levels of the respective cutters 124 and125. The passageway 126 opens downwardly at 130 adjacent the lowercutters 123. Fluid forced downwardly through the passageway 126 willdischarge at the opening 130 and from the tubes 128 and 129 to clearcuttings adjacent the respective bits or cutters.

An eductor collar 131 includes a flange 132 bolted to the supportingflange 133 of the drill bit housing 122. An interior tube 134communicates with the passageway 126 and extends upwardly coaxiallywithin the eductor collar 131 defining an outer passageway 135, having ablind lower end 135'. The tube 134 terminates at the upper end thereofin a box collar 136 which is spaced upwardly from the flange 132 adistance which will result in the upward displacement of the inner tubejoints with respect to the outer tube joints for access to said innertube joints when breaking down or building up the drill string, as notedabove with respect to the drill bit 55.

A sweep tube 137 is secured to the eductor collar 131 and communicateswith the outer passageway 135 at one end 138 thereof. The other end 139of the sweep tube opens downwardly and sweeps within the area 140 ofhigh turbulence near the cutters. By controlling the pressure in thewell bore 141, the discharge from the passageway 125 together withcuttings may be urged through the sweep tube end 139 into the outerpassageway 135 and then upwardly through the outer string passageway 142formed by a modified outer drill string section 143 and communicatingwith the passageway 135 at 144. The modified outer drill string section143 has a weight 145 secured thereto having an upper conical surface 146to aid in withdrawing the drill bit and a lower flange 147 secured bybolts to an upper flange 148 of the eductor collar.

It is to be understood that while certain forms of this invention havebeen illustrated and described, it is not to be limited to the specificmethod or arrangement of parts herein described and shown except insofaras such limitations are included in the claims.

What I claim and desire to secure by Letters Patent is:

1. In combination with earth drilling apparatus a vertical elongatedkelly, a rotary drive table through which said kelly extends forrotating same, said kelly having an outer non-circular pipe engagingsaid drive table and an inner pipe of smaller diameter than the insidedimensions of said kelly outer pipe and extending longitudinally withinsaid kelly outer pipe forming inner and outer concentric flowpassageways within said kelly, said kelly outer pipe terminating at thelower end thereof in a drill string coupling collar, said kelly innerpipe terminating at the lower end thereof in a conduit string couplingcollar, said kelly inner pipe having a longitudinally telescoping sealedjoint spaced above said latter coupling collar permitting thelongitudinal positioning of said latter coupling between a firstposition depending below said kelly outer pipe coupling collar and asecond position spaced above said kelly outer pipe coupling collar.

2. Earth drilling apparatus including a vertically extending dual pipestring, said dual pipe string comprising a plurality of connected outerpipes and a plurality of connected inner pipes of smaller outsidediameter than the inside diameter of said outer pipes and containedwithin said outer pipes, said outer pipes each terminating at the upperand lower ends thereof in outer pipe coupling members, said inner pipeseach terminating at the upper and lower ends thereof in inner pipecoupling members, said inner pipes individually being longitudinallys-lidable and rotatable with respect to adjacent outer pipes, means forlongitudinally positioning said inner pipes with respect to said outerpipes whereby the uncoupling of a pair of outer pipe coupling membersexposes a coupled pair of inner pipe coupling members for grasping, adual kelly having an outer pipe with a lower coupling member normallycoupled to said connected cuter pipes, said dual kelly having an innerpipe with a lower coupling member coupled to said connected inner pipesand normally positioned above said outerpipe lower coupling member, anda longitudinal sliding seal structure cooperating between said kellyinner and outer pipes permitting longitudinal displacement between saidkelly inner and outer pipes for exposing said inner pipe lower couplingmember below said outer pipe lower coupling member when said kelly outerpipe coupling member is uncoupled.

References Cited by the Examiner UNITED STATES PATENTS Canfield 175-215Covender 175-320 Steele 17570 Thompson 175320 Murphy 175215 CHARLES E.OCONNELL, Primary Examiner. J. A. LEPPINK, Assistant Examiner.

1. IN COMBINATION WITH EARTH DRILLING APPARATUS A VERTICAL ELONGATEDKELLY, A ROTARY DRIVE TABLE THROUGH WHICH SAID KELLY EXTENDS FORROTATING SAME, SAID KELLY HAVING AN OUTER NON-CIRCULAR PIPE ENGAGINGSAID DRIVE TABLE AND AN INNER PIPE OF SMALLER DIAMETER THAN THE INSIDEDIMENSIONS OF SAID KELLY OUTER PIPE AND EXTENDING LONGITUDINALLY WITHINSAID KELLY OUTER PIPE FORMING INNER AND OUTER CONCENTRIC FLOWPASSAGEWAYS WITHIN SAID KELLY, SAID KELLY OUTER PIPE TERMINATING AT THELOWER END THEREOF IN A DRILL STRING COUPLING COLLAR, SAID KELLY INNERPIPE TERMINATING AT THE LOWER END THEREOF IN A CONDUIT STRING COUPLINGCOLLAR, SAID KELLY INNER PIPE HAVING A LONGITUDINALLY TELESCOPING SEALEDJOINT SPPACED ABOVE SAID LATTER COUPLING COLLAR PERMITTING THELONGITUDINAL POSITIONING OF SAID LATTER COUPLING BETWEEN A FIRST